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Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

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Pull percpu updates from Tejun Heo:
 "Nothing too exciting.  percpu_ref is going through some interface
  changes and getting new features with more changes in the pipeline but
  given its young age and few users, it's very low impact"

* 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
  percpu-refcount: implement percpu_ref_tryget()
  percpu-refcount: rename percpu_ref_tryget() to percpu_ref_tryget_live()
  percpu: Replace __get_cpu_var with this_cpu_ptr
This commit is contained in:
Linus Torvalds 2014-06-09 14:56:07 -07:00
commit 68a29ef2e3
3 changed files with 35 additions and 3 deletions
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2
include/linux/cgroup.h
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@ -101,7 +101,7 @@ static inline bool css_tryget(struct cgroup_subsys_state *css)
{
if (css->flags & CSS_ROOT)
return true;
return percpu_ref_tryget(&css->refcnt);
return percpu_ref_tryget_live(&css->refcnt);
}
/**

34
include/linux/percpu-refcount.h
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@ -121,6 +121,36 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
* percpu_ref_tryget - try to increment a percpu refcount
* @ref: percpu_ref to try-get
*
* Increment a percpu refcount unless its count already reached zero.
* Returns %true on success; %false on failure.
*
* The caller is responsible for ensuring that @ref stays accessible.
*/
static inline bool percpu_ref_tryget(struct percpu_ref *ref)
{
unsigned __percpu *pcpu_count;
int ret = false;
rcu_read_lock_sched();
pcpu_count = ACCESS_ONCE(ref->pcpu_count);
if (likely(REF_STATUS(pcpu_count) == PCPU_REF_PTR)) {
this_cpu_inc(*pcpu_count);
ret = true;
} else {
ret = atomic_inc_not_zero(&ref->count);
}
rcu_read_unlock_sched();
return ret;
}
/**
* percpu_ref_tryget_live - try to increment a live percpu refcount
* @ref: percpu_ref to try-get
*
* Increment a percpu refcount unless it has already been killed. Returns
* %true on success; %false on failure.
*
@ -128,8 +158,10 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
* will fail. For such guarantee, percpu_ref_kill_and_confirm() should be
* used. After the confirm_kill callback is invoked, it's guaranteed that
* no new reference will be given out by percpu_ref_tryget().
*
* The caller is responsible for ensuring that @ref stays accessible.
*/
static inline bool percpu_ref_tryget(struct percpu_ref *ref)
static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
{
unsigned __percpu *pcpu_count;
int ret = false;

2
include/linux/percpu.h
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@ -29,7 +29,7 @@
*/
#define get_cpu_var(var) (*({ \
preempt_disable(); \
&__get_cpu_var(var); }))
this_cpu_ptr(&var); }))
/*
* The weird & is necessary because sparse considers (void)(var) to be